Hexagonal type barium titanate powder, producing method thereof, dielectric ceramic composition and electronic component

ABSTRACT

Dielectric ceramic composition includes a hexagonal type barium titanate as a main component shown by a generic formula of (Ba 1-α M α ) A (Ti 1-β Mn β ) B O 3  and having hexagonal structure wherein an effective ionic radius of 12-coordinated “M” is −20% or more to +20% or less with respect to an effective ionic radius of 12-coordinated Ba 2+  and the A, B, α and β satisfy relations of 1.000&lt;(A/B)≦1.040, 0≦α&lt;0.003, 0.03≦β≦0.2, and as subcomponents, with respect to the main component, certain contents of alkaline earth oxide such as MgO and the like, Mn 3 O 4  and/or Cr 2 O 3 , and CuO and Al 2 O 3  and rare earth element oxide and glass component including SiO 2 . According to the present invention, it can be provided the hexagonal type barium titanate powder and the dielectric ceramic composition which are preferable for producing electronic components such as a capacitor and the like showing comparatively high specific permittivity, having advantageous insulation property and having sufficient reliability.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a hexagonal type barium titanatepowder, a producing method thereof and a dielectric compositionincluding the hexagonal type barium titanate as a main component, moreprecisely, relates to a dielectric ceramic composition which ispreferable to produce a dielectric layer of electronic components usedfor temperature compensation. Also, the present invention relates to anelectronic component having a dielectric layer composed of thedielectric ceramic composition.

2. Description of the Related Art

Among ceramic capacitors as an example of electronic components, some isused for temperature compensation purpose. For capacitors used for suchpurpose, it is required that change of characteristics such as specificpermittivity and the like in a wide temperature range is small.

As for dielectric material of such capacitors, for example, a materialbased on paraelectrics such as (Ca) (Ti, Zr)O₃ is used (refer toJapanese Patent No. 4325900). However, because based on theparaelectrics, a comparatively high specific permittivity cannot beobtained. For example, when using dielectric material disclosed inJapanese Patent No. 4325900, specific permittivities resulted in 50 orless. Therefore, there is a limitation of increasing a capacitorcapacity.

In the meantime, as for a new material having comparatively highspecific permittivity, for example, hexagonal barium titanate can beexemplified. Although the hexagonal barium titanate has lower specificpermittivity than the barium titanate having perovskite type crystalstructure (tetragonal, cubic), it shows higher permittivity than theparaelectrics.

However, in a crystal structure of the barium titanate, hexagonalstructure is a metastable phase, normally, it can be exist only at 1460°C. or higher. Therefore, in order to obtain the hexagonal bariumtitanate at room temperature, it is necessary to cool rapidly from thehigh temperature of 1460° C. or higher.

In this case, a specific surface area of the obtained hexagonal bariumtitanate becomes 1 m²/g or less because of the rapid cooling from thehigh temperature, thus a coarse powder is only obtained. When producingelectronic components with thinner dielectric layer by using such coarsepowder, there is a problem that it cannot maintain the sufficientreliability, because the powder fails to adapt to the thinner dielectriclayer.

By the way, as for a producing method of the hexagonal bariumtitanate,for example, Non-Patent Literature 1 discloses that BaCO₃, TiO₂ andMn₃O₄ are used as starting raw materials and are heat-treated. By thismeans, a transformation temperature to hexagonal phase can be lowered,hexagonal barium titanate in which Mn is solid-soluted is obtained by aheat treatment at a temperature lower than 1460° C.

However, specific surface area of the hexagonal barium titanate obtainedin the Non-Patent Document 1 is approximately 1.6 m²/g, thus it isinsufficient for applying a thinner dielectric layer in the electroniccomponents even though using this hexagonal barium titanate powder.

-   Non-Patent Literature 1 is “Properties of Hexagonal    Ba(Ti_(1-x)Mn_(x))O₃ Ceramics: Effects of Sintering Temperature and    Mn Content”, Japanese Journal of Applied Physics, 2007 Vol. 46 No.    5A 2978-2983.

BRIEF SUMMARY OF THE INVENTION

The present invention has been made by considering such situations and apurpose of the invention is to provide a hexagonal type barium titanatepowder and a dielectric ceramic composition which are preferable toproduce a dielectric layer of electronic components such as ceramiccapacitor and the like showing comparatively high specific permittivity,having advantage insulation property and having sufficient reliability.

In order to achieve the above mentioned purposes, according to keenexamination by the present inventors, they have found the electroniccomponents such as ceramic capacitor and the like improving specificpermittivity of the dielectric layer, having advantage insulationproperty and having sufficient reliability can be obtained by composinga main phase of the dielectric ceramic composition of hexagonal typebarium titanate having specific composition so that the presentinvention has been completed.

Namely, a hexagonal type barium titanate powder according to the presentinvention includes a barium titanate as a main component shown by ageneric formula of (Ba_(1-α)M_(α))_(A)(Ti_(1-β)Mn_(β))_(B)O₃ and havinghexagonal structure wherein an effective ionic radius of 12-coordinated“M” is −20% or more to +20% or less (within ±20%) with respect to aneffective ionic radius of 12-coordinated Ba²⁺, and the A, B, α and βsatisfy relations of 1.000<(A/B)≦1.040, 0≦α<0.003, 0.003≦β≦0.2.

In the barium titanate powder according to the present invention, bariumtitanate powder having hexagonal structure (hexagonal barium titanate)is included as a main component. Specifically, hexagonal barium titanatemay be included in a content of 50 mass % or more with respect to 100mass % of hexagonal barium titanate powder according to the presentinvention.

In the crystal structure of the barium titanate, the hexagonal structureis high temperature stable phase, and exists only at 1460° C. or higher.Therefore, in order to maintain the hexagonal structure at roomtemperature, it is necessary to cool rapidly from 1460° C. to near theroom temperature. When it is rapidly cooled through such the widetemperature range, the hexagonal barium titanate powder obtained afterthe rapid cooling becomes coarse, and its specific surface area becomes,for example, 1 m²/g or less.

The specific surface area and an average particle diameter of powder arein inverse relationship, thus the specific surface area thereof issubstituted in terms of the average particle diameter, it becomes, forexample, 1 μm or more. On the other hand, in order to keep reliabilitysufficiently as electronic components, it is preferable that two or moredielectric particles are placed between the dielectric layers.Therefore, when powder having small specific surface area is used, itbecomes difficult to make the dielectric layer thinner.

However, as mentioned above, in the crystal structure, thetransformation temperature to hexagonal structure can be lowered bysubstituting a position where Ti occupies (B site) by Mn in a certainratio. Namely, it is possible to maintain the hexagonal structure evenat lower temperature than 1460° C., as a result, the specific surfacearea can be increased comparatively.

In addition to this, in the present invention, a range of an abundanceratio (A/B) of an element existing at the position where Ba occupies (Asite) and an element existing at the position where Bi occupies (B site)is set as above.

By controlling the A/B as above range, grain growth of the bariumtitanate particle can be suppressed. As a result, the specific surfacearea of the obtained hexagonal barium titanate powder can be increasedfurther. Specifically, hexagonal barium titanate powder having 2 m²/g ormore of the specific surface area can be obtained.

Note that, the A site may be substituted by the element “M” within theabove range. Namely, elements other than Ba may occupy the A siteposition.

Preferably, a ratio of the α and β satisfies relation of (α/β)≦0.40,more preferably (α/β)≦0.07. The “α/β”, which shows a ratio of an amountthat the A site is substituted by the element “M” (A site substitutedamount) and an amount that the B site is substituted by the Mn (B sitesubstituted amount) is set as the above range, an effect of the presentinvention can be improved further.

Also, a dielectric ceramic composition according the present inventionincludes a hexagonal type barium titanate as a main component shown by ageneric formula of (Ba_(1-α)M_(α))_(A)(Ti_(1-β)Mn_(β))_(B)O₃ and havinghexagonal structure wherein an effective ionic radius of 12-coordinated“M” is −20% or more to +20% or less (within ±20%) with respect to aneffective ionic radius of 12-coordinated Ba²⁺, and the A, B, α and βsatisfy relations of 1.000<(A/B)≦1.040, 0≦α<0.003, 0.03≦β≦0.2, and, assubcomponents, with respect to 100 moles of the main component, 2 to 5moles of at least one of alkaline earth oxide selected from a groupconsisting of MgO, CaO and BaO in terms of respective oxides, and atotal amount of the alkaline earth oxides is 15 moles or less, 0.5 to 2moles of Mn₃O₄ and/or Cr₂O₃, and CuO and Al₂O₃ in terms of respectivemetal elements, 1 to 5 moles of at least one of oxides of rare earthelement selected from a group consisting of Y, La, Ce, Pr, Nd, Sm, Gd,Tb, Dy, Ho and Yb in terms of total of rare earth element, and 0.1 to 1mole of glass component including SiO₂ in terms of SiO₂.

Also, an electronic component according to the present invention has adielectric layer composed of the above mentioned dielectric ceramiccomposition and an internal electrode layer.

Also, a method of producing the hexagonal type barium titanate powderaccording to the present invention includes steps of preparing at leasta raw material of barium titanate and a raw material of Mn, andheat-treating the raw material of the barium titanate and the rawmaterial of Mn.

According to the present invention, the hexagonal type barium titanateand the dielectric ceramic composition which are preferable to producedielectric layer of electronic components such as ceramic capacitor andthe like showing comparatively high specific permittivity, havingadvantageous insulation property and having sufficient reliability canbe obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a multilayer ceramic capacitor according to one embodiment ofthe present invention.

FIG. 2A to FIG. 2C are X-ray diffraction chart of samples of examplesand comparative examples according to the present invention.

FIG. 3 is a graph showing particle size distribution of samples ofexamples and comparative examples according to the present invention.

FIG. 4 shows temperature dependency of the specific permittivity of amultilayer ceramic capacitor according to one embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Below, the present invention will be explained based on embodimentsshown as follows.

(Multilayer Ceramic Capacitor)

As shown in FIG. 1, a multilayer ceramic capacitor 1 as a representativeexample of electronic components has a capacitor device body 10 whereina dielectric layer 2 and an internal electrode layer 3 are alternatelystacked. At the both end portions of the capacitor device body 10, apair of external electrodes 4 connected with internal electrode layers 3alternately stacked inside the device body 10, is formed. The shape ofthe capacitor device body 10 is not particularly limited, and isnormally rectangular parallelepiped. Also, its dimension is notparticularly limited, and may be properly changed as usage.

The internal electrode layers 3 are stacked so that each end face isalternately exposed to surfaces of the two opposed end portions of thecapacitor device body 10. Also, the pair of external electrodes 4 isformed at both end portions of the capacitor device body 10, andconnected with the exposed end faces of the alternately-stacked internalelectrode layers 3 to form a capacitor circuit.

The dielectric layer 2 includes a dielectric ceramic compositionaccording to the present embodiment. The dielectric ceramic compositionaccording to the present embodiment has a main phase composed ofhexagonal type barium titanate, and includes specific subcomponents.Note that, although compositional formulas of various oxides are shownin the following, the amount of oxygen (O) can be slightly deviate fromthe above stoichiometric constitution.

Firstly, it will be explained with respect to the hexagonal type bariumtitanate which is a main component and constitutes a main phase of thedielectric ceramic composition according to the present embodiment. Themain phase composed of the hexagonal type barium titanate is formed byusing following mentioned hexagonal type barium titanate powder as a rawmaterial and firing thereof with subcomponents.

(Hexagonal Type Barium Titanate Powder)

The hexagonal type barium titanate powder according to the presentembodiment has barium titanate powder having hexagonal structure(hexagonal barium titanate) as a main component. Specifically, 50 mass %or more, preferably 90 mass % or more, further preferably 95 mass % ormore of hexagonal barium titanate is included with respect to 100 mass %of the hexagonal type barium titanate powder according to the presentembodiment.

Note that, in the hexagonal type barium titanate powder according to thepresent embodiment, barium titanate having tetragonal structure or cubicstructure may be included other than the hexagonal barium titanate.

The hexagonal type barium titanate powder according to the presentembodiment can be shown by using a generic formula of(Ba_(1-α)M_(α))_(A)(Ti_(1-β)Mn_(β))_(B)O₃.

The α in the above formula shows a substitution ratio of an element “M”with respect to Ba (content of the “M” in the hexagonal barium typetitanate powder), it is 0≦α<0.003, preferably 0≦α≦0.002. When thecontent of the “M” is too large, a transformation temperature to thehexagonal structure becomes higher, thus powder having large specificsurface area tends not to be obtained.

In the hexagonal structure, the Ba occupies an “A” site position asBa²⁺. The element “M” may substitute the Ba in the above mentioned rangeand exist at the “A” site position, and the “A” site may be occupied byBa only. Namely, the element “M” may not be included in the hexagonalbarium titanate.

The “M” has an effective ionic radius (12-coordinated) of −20% or moreto +20% or less (within ±20%) with respect to an effective ionic radiusof 12-coordinated Ba²⁺ (1.61 pm). The Ba can be substituted easily by“M” having such effective ionic radius.

Specifically, as for the element “M”, it is preferably at least oneselected from Ca, Sr, Dy, Gd, Ho, Y, Er, Yb, La, Ce and Bi. The element“M” may be selected depending on desired properties.

The β in the above formula shows a substitution ratio of Mn with respectto Ti (content of Mn in the hexagonal type barium titanate powder), itis 0.03≦β≦0.20, preferably 0.05≦β≦0.15. When the content of the Mn istoo small or too large, powder having large specific surface area tendsnot to be obtained, because a transformation temperature to hexagonalstructure becomes higher.

In the hexagonal structure, although the Ti occupies a “B” site positionas Ti⁴⁺, in the present embodiment, the Mn substitutes the Ti in theabove mentioned range and exists at the “B” site position. Namely, theMn is solid-soluted in the barium titanate. By existing the Mn at the“B” site position, the trans forming temperature from tetragonal/cubicstructure to the hexagonal structure in the barium titanate can belowered.

The “A” and “B” in the above formula respectively show a ratio ofelements (Ba and M) occupying the “A” site and a ratio of elements (Tiand Mn) occupying the “B” site. In the present embodiment, a ratio of(A/B) is 1.000<A/B≦1.040, preferably 1.006≦A/B≦1.036.

When A/B is too small, reactivity at time of generating the bariumtitanate becomes high so that it will be easy to fasten particle growthto temperature. Therefore, it is hard to obtain a fine particle and thusdesired specific surface area tends not to be obtained. On the contrary,when A/B is too large, it is not preferable because an occupying ratioof Ba becomes larger so that Ba-rich barium orthotitanate (Ba₂TiO₄)tends to generate as a phase different from that of barium titanate.

The hexagonal type barium titanate powder according to the presentembodiment has the above mentioned constitution, and is produced byfollowing specified method. Therefore, when the specific surface areaimmediately after producing is measured by BET method, it becomes 2 m²/gor more, preferably 3 m²/g or more, further preferably 4 m²/g or more.

As a result, for example, even in case the that dielectric layer of amultilayer ceramic electronic component is made thinner (e.g., thicknessof interlayer: 1 μm), a number of the barium titanate particle placedbetween the interlayer can be at least 2 or more so that sufficientreliability (high temperature load lifetime) can be maintained.

Note that, although the specific surface area can be increased bypulverizing the obtained powder with using a ball mill and the like, inthis case, particle size distribution becomes broader. As a result,deviation of particle size is larger and deviation of reliability islarger, which is not preferable. Also, an impact (energy) and the likeadded to the powder when pulverizing gives an adverse effect to thepowder, which is not preferable. Therefore, it is preferable that thespecific surface area thereof is larger at a condition when thehexagonal barium titanate is generated.

Note that, the effective ionic radi described in the presentspecification are the values based on a literature “R. D. Shannon ActaCrystallogr., A32, 751 (1967)”.

(Producing Method of Hexagonal Type Barium Titanate Powder)

Next, a method of producing hexagonal type barium titanate powderaccording to the present embodiment will be explained.

Firstly, a raw material of barium titanate and a raw material of Mn areprepared. A raw material of element “M” may be prepared if needed.

As for the raw material of the barium titanate, barium titanate(BaTiO₃), oxides (BaO, TiO₂) composing barium titanate and mixturethereof may be used. Further, it is possible to properly select fromvarious other compounds to become the above-mentioned oxides orcomposite oxides by firing, for example, carbonate, oxalate, nitrate,hydroxide, organic metallic compounds, etc., to use by mixing.Specifically, as for a raw material for the barium titanate, BaTiO₃ maybe used, BaCO₃ and TiO₂ may be used. In the present embodiment, BaCO₃and TiO₂ are preferably used.

Note that, when BaTiO₃ is used for the raw material of the bariumtitanate, it may be barium titanate having tetragonal structure, bariumtitanate having cubic structure or barium titanate having hexagonalstructure. Also, it may be mixture thereof.

Specific surface areas of the above mentioned raw materials arepreferably 5 to 100 m²/g, more preferably 10 to 50 m²/g. As for ameasuring method for the specific surface area, although it is notparticularly limited, for example, BET method is exemplified.

Also, as for a raw material of the Mn, compounds of the Mn may be used,for example, it is possible to properly select from oxides, carbonate,oxalate, nitrate, hydroxide and organic metallic compounds, etc., to useby mixing. As for a raw material of the element “M”, it may be used in asimilar manner with the raw materials of the Mn.

Specific surface areas of these raw materials are preferably 5 to 50m²/g, further preferably 10 to 20 m²/g.

Next, the prepared raw materials are mixed after weighing so as to be apredetermined compositional ratio, and mixture of raw materials isobtained, if needed, by pulverizing. As for methods of mixing andpulverizing, for example, it can be exemplified a wet method for mixingand pulverizing wherein the raw materials are put into a conventionallyknown grinding container such as a ball mill and the like with solventsuch as water, etc. Also, it may be mixed and pulverized by a dryingmethod wherein a drying mixer, etc. is used. At this time, in order toimprove dispersibility of the inputted raw materials, it is preferableto add a dispersing agent. As for the dispersing agent, conventionallyknown agent may be used.

Next, heat-treatment is performed to the obtained mixture of rawmaterials after drying if needed. A temperature rising rate at theheat-treatment is preferably 50 to 900° C./h. Also, a holding time atthe heat-treatment may be set as higher than a transforming temperatureto a hexagonal structure. In the present embodiment, the transformationtemperature is below 1460° C., and it changes depending on A/B, “A” sitesubstitution amount (α) and “B” site substitution amount (β), etc., thusthe holding temperature can be changed depending on these. In order toincrease a specific surface area of the powder, for example, it ispreferably set as 1050 to 1300° C. A holding time is preferably 0.5 to 5hours, further preferably 2 to 4 hours.

By performing the heat-treatment, Mn is solid-soluted in BaTiO₃, Tipositioned at “B” site can be substituted by the Mn. As a result, thetransforming temperature to the hexagonal structure can be lower thantemperature at the heat-treatment, the hexagonal type barium titanatecan be generated easily. Also, when the element “M” is included, the “M”is solid-soluted in BaTiO₃ so as to substitute Ba at “A” site position.

Note that, when the holding temperature is too low, non-reacted and/orinsufficient-reacted raw material (for example, BaCO₃ and the like)tends to be generated as a phase different from BaTiO₃.

Then, after passing the holding time of the heat-treatment, it is cooledfrom the holding temperature of the heat-treatment to room temperatureso as to maintain hexagonal structure. Specifically, the cooling rate ispreferably set as 200′C/h or more.

By performing this, hexagonal type barium titanate powder, whichincludes hexagonal barium titanate as a main component wherein hexagonalstructure is maintained at room temperature, can be obtained. Althoughit is not particularly limited to examine as to whether the obtainedpowder is hexagonal type barium titanate powder or not, in the presentembodiment, it is examined by X-ray diffraction method.

Firstly, it is examined as to whether a peak other than a peakoriginated from barium titanate (hexagonal, cubic, tetragonal) exists ornot by a X-ray diffraction chart obtained by the X-ray diffractionmethod. If such peak exists, it is not preferable because the phasedifferent from BaTiO₃ (Ba₂TiO₄, BaCO₃ and the like) is generated in theobtained powder.

When the phase different from BaTiO₃ is not generated, namely, theobtained powder is composed of barium titanate (BaTiO₃) only, it isexamined by calculating a generating ratio of the hexagonal bariumtitanate. Specifically, a total of maximum peak intensities of hexagonalbarium titanate, tetragonal barium titanate and cubic barium titanate isdefined as 100%, a ratio that occupies the maximum peak intensity of thehexagonal barium titanate is defined as a generating ratio (abundanceratio) of the hexagonal barium titanate. When this ratio is 50% or more,the hexagonal type barium titanate powder which includes the hexagonalbarium titanate as a main component can be obtained.

The hexagonal type barium titanate powder can be obtained by coolingfrom a temperature lower than a temperature at which hexagonal bariumtitanate stably exists normally (1460° C. or higher), thus it can beobtained as fine particle. Further, because composition and A/B ratio,etc. of the hexagonal type barium titanate are controlled within theabove range, further fine particle can be obtained. Specifically, thespecific surface area of the hexagonal type barium titanate according tothe present embodiment is preferably 2 m²/g or more, more preferably 3m²/g or more, further preferably 4 m²/g or more.

Note that the above mentioned specific surface area is a value when theobtained hexagonal type barium titanate powder is generated, also it hasextremely sharp particle size distribution and a single peak.

Electronic components having dielectric layers and electrode layers areproduced by using the hexagonal type barium titanate powder obtained bythe above manner and following mentioned subcomponents.

(Subcomponents)

As for subcomponents, at least one of alkaline earth oxide selected froma group consisting of MgO, CaO and BaO, as metal oxides, Mn₃O₄ and/orCr₂O₃, and CuO and Al₂O₃, and oxides of at least one of rare earthelement selected from a group consisting of Y, La, Ce, Pr, Nd, Sm, Gd,Tb, Dy, Ho and Yb, and glass component including SiO₂ are used.

The MgO and the like have an effect to make flatteningcapacitance-temperature characteristic. In the present embodiment,content of at least one of alkaline earth oxides selected from the groupconsisting of MgO, CaO and BaO in terms of respective oxides is 2 to 5moles, preferably 2 to 3 moles with respect to 100 moles of the maincomponent. Here the content of the alkaline earth oxide is not a totalof the respective oxides, it means contents of the respective oxides.Also, as far as the MgO, CaO and BaO in terms of oxide respectively areused in a range of 2 to 5 moles, it can be used as single kind alone, ormay be used by combining two kinds or more. For example, an embodimentwherein 5 moles of MgO, 5 moles of CaO and 5 moles of BaO are used isincluded in a scope of the present invention. On the other hand, anembodiment wherein 1 mole of MgO, 1 mole of CaO and 1 mole of BaO areused is not included in the scope of the present invention, although atotal content is within a range of 2 to 5 moles. Also, an embodimentwherein 2 moles of MgO, 1 mole of CaO and 1 mole of BaO are used isincluded in the scope of the present invention because the contents ofthe CaO and BaO is within a range of 2 to 5 moles.

Further, in addition to satisfy the above range, a total content of theMgO, CaO and BaO in terms of oxides is within a range of 15 moles orless, preferably 7 to 12 moles, further preferably 8 to 10 moles. Forexample, an embodiment wherein 5 moles of MgO, 5 moles of CaO and 6moles of BaO are used is not included in the embodiment of the presentinvention because a total content of the MgO, CaO and BaO becomes 16moles, although contents of MgO and CaO are within a range of 2 to 5moles.

Metal oxides such as Mn₃O₄ have effects of improving sintering, makinginsulation resistance (IR) higher and improving IR lifetime. In thepresent embodiment, respective contents of Mn₃O₄ and/or Cr₂O₃, and CuOand Al₂O₃ in terms of respective metal element are 0.5 to 2 moles,preferably 1 to 1.5 moles with respect to 100 moles of the maincomponent. Here, the content of the above mentioned metal oxides are nota total of the respective oxides, it means the contents of therespective oxides. Also, the contents are defined in terms of metalelement not in terms of metal oxide. For example, when using 1 mole ofAl₂O₃, it means 2 moles in terms of Al element is used. Also, unlike theabove mentioned alkaline earth oxides, Mn₃O₄ and/or Cr₂O₃, and CuO andAl₂O₃ are respectively used as 0.5 to 2 moles in terms of metal element.For example, an embodiment wherein 1 mole of Mn₃O₄ (3 moles of Mnelement), 0.5 mole of CuO (0.5 mol of Cu element) and 0.8 mole of Al₂O₃(1.6 mol of Al element) are used is not included in the scope of thepresent invention because the content of the Mn₃O₄ is out of the rangedefined in the present invention.

Although a total content of the Mn₃O₄ and/or Cr₂O₃, and CuO and Al₂O₃ isnot particularly limited, preferably within a range of 2 to 5 moles,more preferably 3 to 4 moles.

Content of oxides of at least one of rare earth element selected from agroup consisting of Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Yb interms of rare earth element in total is 1 to 5 moles, preferably 1.5 to4 moles. As for the rare earth element oxides, oxides of Y, Gd, Tb, Dy,Ho or Yb are preferably used. These rare earth elements may be used as asingle kind alone, also, they may be used as combined, and similareffects can be obtained. When the content of the rare earth elementoxide is less than 1 mole, effects of improving reliability(acceleration lifetime) cannot be obtained. Also, when the content ofthe rare earth oxides excesses 5 moles, sinterability is reduced thusfiring temperature tends to be higher.

Glass component including SiO₂ is added as sintering aid. Although theglass component is not particularly limited as far as SiO₂ is included,it may be an amorphous complex oxide wherein SiO₂ is complexed with anyone of ZnO, B₂O₃ and Al₂O₃.

Content of the glass component including SiO₂ in terms of SiO₂ is 0.1 to1 mole, preferably 0.5 to 0.8 mol, further preferably 0.7 to 0.8 molwith respect to 100 moles of the main component. When the content of theglass component is less than 0.1 mole, it does not work as sinteringaid. Also, when the content of the glass component excesses 1 mole, thespecific permittivity is reduced and a voltage withstanding alsodeteriorates. Further, a voltage dependence of the insulation resistancetends to become larger.

Also, other subcomponents may be added to the above mentioned dielectricceramic composition within a range which is available to achieve thepurpose of the present invention.

(Multilayer Ceramic Capacitor)

Although a thickness of a dielectric layer 2 in a multilayer ceramiccapacitor 1 shown in FIG. 1 which is a representative example ofelectronic components is not particularly limited, it is preferable 5 μmor less per one layer, more preferably 3 μm or less. Although a lowerlimit of the thickness is not particularly limited, for example, it isapproximately 1 μm. Due to the dielectric ceramic composition accordingto the present embodiment, 50 or more of specific permittivity is shownwith 1 μm or more of thickness. Although a number of stacked layers isnot particularly limited, it is preferable 200 or more.

An average crystal particle diameter of dielectric particle included inthe dielectric layer 2 is not particularly limited, it may be determinedfrom, for example, a range of 0.1 to 1 μm, preferably 0.1 to 0.5 μmdepending on the thickness of the dielectric layer 2. Note that, theaverage crystal particle diameter included in the dielectric layer ismeasured as follows. Firstly, the obtained capacitor sample is cut witha vertical plane to an internal electrode, the cut face is polished.Then, chemical etching is performed to the polished face, after this, itis observed by a scanning electron microscope (SEM), and calculated by acode method with assuming a shape of the dielectric particulate issphere.

Although conducting material included in an internal electrode layer 3is not particularly limited, base metals can be used because thematerial constituting the dielectric layer 2 has reduction toresistance. As for the base metals used for the conducting material, Nior Ni alloy is preferable. As for the Ni alloy, an alloy of at least onekinds of element selected from Mn, Cr, Co and Al with Ni is preferable,and Ni content in the alloy is preferably 95 wt % or more.

Although conducting material included in an external electrode 4 is notparticularly limited, in the present embodiment, inexpensive Ni, Cu andtheir alloys may be used. A thickness of the external electrode 4 may bedetermined depending on a purpose of use, in normally, it is preferableabout 10 to 50 μm.

A multilayer ceramic capacitor in which the dielectric ceramiccomposition of the present embodiment is used, is produced by, assimilar with a conventional multilayer ceramic capacitor, producing agreen chip by a normal printing method or sheet method using a paste,then firing thereof, and firing after printing or transferring anexternal electrode. Below, a method of producing will be explainedspecifically.

Firstly, dielectric ceramic composition powder included in dielectriclayer paste is prepared. Specifically, a raw material of main componentand a raw material of subcomponent are mixed by a ball mill and the likeso that a dielectric ceramic composition powder is obtained.

As for a raw material of the main component, the above mentionedhexagonal type barium titanate powder is used. As for raw materials ofthe subcomponents, although the above mentioned oxide and mixturethereof, complex oxides thereof can be used, other than these, variouskinds of compounds which becomes the above mentioned oxide and complexoxide by firing, for example, suitably selected from carbonate, oxalate,nitrate, hydroxide, organometallic compounds can be used by mixing too.

Content of the respective compounds in the obtained dielectric ceramiccomposition powder may be determined so that it satisfies composition ofthe above mentioned dielectric ceramic composition after firing.

Calcining and the like may be further performed to the above mentionedmain component and subcomponents. Note that, as for the calciningcondition, for example, a calcining temperature may be set as preferably800 to 1100° C., a calcining time may be set as preferably 1 to 4 hours.

Then, the obtained dielectric ceramic composition powder is made into apaste to prepare the dielectric layer paste. The dielectric layer pastemay be an organic paste kneaded with dielectric ceramic compositionpowder and the organic vehicle, or it may be a water-based paste.

The organic vehicle is obtained by dissolving a binder in an organicsolvent. The binder used in the organic vehicle is not particularlylimited, and may be properly selected from a variety of usual binderssuch as ethylcellulose and polyvinyl butyral. Also, the organic solventused is not particularly limited, and may be properly selected from avariety of organic solvents such as terpineol, butyl carbitol, acetoneand toluene in accordance with a method used such as a printing methodand sheet method.

Also, when using water-based dielectric layer paste, dielectricmaterials can be kneaded with a water-based vehicle obtained bydissolving an aqueous binder and dispersant, etc., in water. The aqueousbinder used for water-based vehicle is not particularly limited, and forexample, polyvinyl alcohol, cellulose, aqueous acrylic resin, etc., maybe used.

An internal electrode layer paste is obtained by kneading conductingmaterials consisting of the above mentioned various conducting metalsand alloys, or various oxides, organic metallic compound and resinate,etc., which become the above-mentioned conducting materials afterfiring, with the above-mentioned organic vehicle.

An external electrode paste may be obtained as with the above-mentionedinternal electrode layer paste.

The content of organic vehicle in each of the above-mentioned paste isnot particularly limited, and may be usual content, for example, 1 to 5wt % or so of the binder and 10 to 50 wt % or so of the solvent. Also,in each paste, there may be included additives selected from a varietyof dispersants, plasticizer, dielectric, insulators, etc., if needed.The total contents of these are preferably 10 wt % or less.

When using the printing method, the dielectric layer paste and theinternal electrode layer paste are printed on a substrate such as PET toform layers, and after cutting to a predetermined shape, a green chip isobtained by removing from the substrate.

Also, when using the sheet method, a green sheet is formed by usingdielectric layer paste, internal electrode layer paste is printedthereon, and then, these are stacked to form a green chip.

Before firing, the green chip is subject to binder removal treatment.The binder removal treatment may be suitably determined depending on thetype of the conducting material in the internal electrode paste. Howeverwhen using base metal such as Ni or Ni alloy as the conducting material,it is preferable that oxygen partial pressure of binder removalatmosphere is set to 10⁻⁴⁵ to 10⁵ Pa. When the oxygen partial pressureis less than the above range, binder removal effect is reduced. Also,when the oxygen partial pressure exceeds the above range, the internalelectrode layer tends to oxidize.

Also, as for the binder removal condition other than this, a temperaturerising rate is preferable 5 to 300° C./hr, more preferably 10 to 100°C./hr, a holding temperature is preferably 180 to 400° C., furtherpreferably 200 to 350° C., a temperature holding time is preferably 0.5to 24 hours, further preferably 2 to 20 hours. Also, firing atmosphereis preferably air or reducing atmospheres, as for an atmospheric gas inthe reducing atmosphere, for example, a wet mixture gas of N₂ and H₂ ispreferably used.

The atmosphere when firing the green chip can be suitably determineddepending on the type of the conducting material in the internalelectrode paste. However when using base metal such as Ni or Ni alloy asthe conducting material, the oxygen partial pressure of the firingatmosphere is preferably 10⁻⁹ to 10⁻⁴ Pa. When the oxygen partialpressure is below the above range, the conducting material of theinternal electrode layer may have abnormal sintering which results in abreakage thereof. Also, when the oxygen partial pressure exceeds theabove range, the internal electrode layer tends to oxidize.

Also, the holding temperature at the firing is preferably 900 to 1200°C., and more preferably 1000 to 1100° C. When the holding temperature isbelow the above range, the densification becomes insufficient; and whenit exceeds the above range, the breakage of the electrode due to theabnormal sinter of the internal electrode layer, the deterioration ofthe capacitance-temperature characteristics due to the dispersion of theconstitution material of the internal electrode layer, or a reduction ofthe dielectric ceramic composition tend to Occur.

As for other firing condition other than the above, a temperature risingrate is preferably 50 to 500° C./hour, more preferably 200 to 300°C./hour, a temperature holding time is preferably 0.5 to 8 hours, morepreferably 1 to 3 hours, a cooling rate is preferably 50 to 500°C./hour, more preferably 200 to 300° C./hour. Also, firing atmosphere ispreferably reducing atmosphere, as for an atmospheric gas in thereducing atmosphere, for example, a wet mixture gas of N₂ and H₂ ispreferably used.

After firing in a reducing atmosphere, it is preferable to anneal thecapacitor device body. The annealing is a treatment for reoxidizing thedielectric layer and can make IR lifetime significantly longer, so thatthe reliability is improved.

The oxygen partial pressure in the annealing atmosphere is preferably10⁻³ Pa or more, particularly preferably 10⁻² to 10 Pa. When the oxygenpartial pressure is below the above range, it may be difficult toreoxidize the dielectric layer. When it exceeds the above range, theinternal electrode layer tends to be oxidized.

Holding temperature at annealing is preferably 1100° C. or less,particularly preferably 500 to 1100° C. When the holding temperature isbelow the above range, the dielectric layer may not be sufficientlyoxidized, often resulting in lowering IR and shortening IR lifetime. Onthe other hand, when the holding temperature exceeds the above range,the internal electrode layer is not only oxidized to reduce thecapacitance, but also reacts with the dielectric body, which may easilycause deteriorated capacitance-temperature characteristics, reduced IR,and reduction in IR lifetime. Note that the annealing may consist of atemperature rising process and temperature cooling process. Namely, thetemperature holding time may be zero. In this case, the holdingtemperature is same as the maximum temperature.

As for other annealing conditions other than the above, the temperatureholding time is preferably 0 to 20 hours, more preferably 2 to 10 hours,and the cooling rate is preferably 50 to 500° C./hour, more preferably100 to 300° C./hour. Also, the atmosphere gas at annealing is preferablya wet N₂ gas, for example.

In the above-mentioned binder removal treatment, firing and annealing, awetter, etc., may be used to wet the N₂ gas and mixed gas, for example.In this case, the water temperature is preferably 5 to 75° C. or so.

The binder removal treatment, firing and annealing may be performedcontinuously or independently.

An end face polishing is conducted to a capacitor body obtained as theabove, for example by barrel polishing or sandblast, an externalelectrode paste is printed or transferred and fired so that an externalelectrode 4 is formed. A firing condition of the external electrodepaste is preferably, for example, about 10 minute to 1 hour at 600 to800° C. in wet mixture gas of N₂ and H₂. Then, if needed, a coatinglayer is formed on a surface of the external electrode 4 by plating andthe like.

The multilayer ceramic capacitor of the present invention producedaccording to the above is used for various electronic components and thelike by mounting on a printed-circuit board and the like by solderingand the like.

The foregoing has described embodiment of the present invention,however, the present invention is not limited to the above mentionedembodiment at all, and various modification can be made within a scopeof the present invention.

For example, in the above-mentioned embodiment, a multilayer ceramiccapacitor is exemplified as an electronic device according to thepresent invention. However, the electronic device according to thepresent invention is not limited to the multilayer ceramic capacitor andmay be any comprising the dielectric layer having the above composition.Also, in the above mentioned embodiment, although the hexagonal typebarium titanate powder according to the present invention is produced byso called a solid phase method, it may be produced by oxalate method,sol-gel method and the like.

EXAMPLES

Below, the present invention will be explained based on further detailedexamples, however, the present invention is not limited to theseexamples. Note that, in the following examples and comparative examples,“specific permittivity/∈”, “insulation resistance” and “Q value” weremeasured as follows.

(Specific permittivity/∈ and insulation resistance)

A capacitance “C” was measured to a capacitor sample, under a criteriontemperature 20° C., a frequency 1 kHz, an input signal level (measuredvoltage) 0.5 Vrms/μm was inputted by a digital LCR meter (YHP4274A madeby Yokogawa Electric Corp.). Then, the specific permittivity (no unit)was calculated based on the obtained capacitance, a thickness of thedielectric body of the multilayer ceramic capacitor and overlapping areaof each internal electrode.

Then, insulation resistance IR was measured after applying 50V of DCduring 60 seconds at 25° C. to the capacitor sample by using aninsulation resistance meter (R8340A made by Advantest Corp.).

(Q Value)

Q value was measured under a condition that temperature 25° C., afrequency 1 kHz, voltage (RMS value) 1 V of AC, by a Q meter.

Experimental Example 1 Preparation of Hexagonal Type Barium TitanatePowder

At first, BaCO₃ (specific surface area: 25 m²/g) and TiO₂ (specificsurface area: 50 m²/g) were prepared as raw materials of bariumtitanate. Also, Mn₃O₄ (specific surface area: 20 m²/g) was prepared as araw material of Mn and La (OH)₃ (specific surface area: 10 m²/g) wasprepared as a raw material of the element “M”.

These raw materials were weighed so that “α”, “β”, “A/B” in a genericformula of (Ba_(1-α)M_(α))_(A)(Ti_(1-β)Mn_(β))_(B)O₃ satisfy the valuesshown in Table 1 respectively and mixed with water and dispersing agentby a ball-mill. The obtained mixed powder was heat-treated underfollowing mentioned heat-treatment condition so that hexagonal typebarium titanate powder was produced.

The heat-treatment condition was that temperature rising rate: 200°C./hr, holding temperature: temperature shown in Table 1, temperatureholding time: 2 hours, cooling rate: 200° C./hr, atmospheric gas: air.

Following mentioned X-ray diffraction was performed to the obtainedhexagonal type barium titanate powder. Also, a specific surface area wasmeasured by BET method. Results of the specific surface area are shownin Table 3.

(X-Ray Diffraction)

For the X-Ray Diffraction, Cu—Kα Ray was Used as a X-Ray source,measuring condition thereof was 45 kV voltage, 2θ=20° to 90° withelectric current 40 mA, scanning speed of 4.0 deg/min, elapsed time of30 seconds.

From X-ray diffraction chart obtained by the measurement, identifyingrespective peaks near 2θ=45°, evaluation was made as to whether bariumtitanate (hexagonal, tetragonal, cubic) and phase different from bariumtitanate exist. Results are shown in Table 1. The X-ray diffractionchart with respect to examples Nos. 10 and 2, and a comparative example9 are shown in FIG. 2A to FIG. 2C.

Next, with respect to samples wherein only peak of barium titanate wasobserved, maximum peak intensities of hexagonal barium titanate(h-BaTiO₃), tetragonal barium titanate (t-BaTiO₃), cubic barium titanate(c-BaTiO₃) were calculated. Then, an occupied ratio of the maximum peakintensity of h-BaTiO₃ to a total of maximum peak intensities ofh-BaTiO₃, t-BaTiO₃ and c-BaTiO₃ were calculated so that a ratio ofhexagonal barium titanate (h-BaTiO₃) was evaluated. Results of theobtained rate were shown in Table 2.

TABLE 1 (Ba_(1−α)La_(α))_(A)(Ti_(1−β)Mn_(β))_(B)O₃ A site B site sub-Identified phase by X-ray diffraction Sample substitution stitutionHeat-treating temperature No. amount α amount β α/β A/B 1000° C. 1050°C. 1100° C. 1150° C. 1200° C. 1250° C. 1300° C. 1350° C. comparative 00.14 0.00 1.000 NG NG h-BT h-BT h-BT h-BT h-BT h-BT example 2 example 10.002 0.14 0.01 1.006 NG NG h-BT h-BT h-BT h-BT h-BT h-BT example 20.002 0.14 0.01 1.008 NG NG h-BT h-BT h-BT h-BT h-BT h-BT example 30.002 0.14 0.01 1.026 NG NG h-BT h-BT h-BT h-BT h-BT h-BT example 40.002 0.14 0.01 1.036 NG NG h-BT h-BT h-BT h-BT h-BT h-BT example 50.002 0.14 0.01 1.040 NG NG NG mixed h-BT h-BT h-BT h-BT phasecomparative 0.002 0.14 0.01 1.085 NG NG NG NG NG NG NG NG example 1example 6 0 0.14 0.00 1.008 NG NG h-BT h-BT h-BT h-BT h-BT h-BT example7 0.0012 0.14 0.01 1.008 NG NG h-BT h-BT h-BT h-BT h-BT h-BT example 20.002 0.14 0.01 1.008 NG NG h-BT h-BT h-BT h-BT h-BT h-BT example 80.0029 0.14 0.02 1.008 NG NG h-BT h-BT h-BT h-BT h-BT h-BT comparative0.07 0.14 0.50 1.008 NG NG NG NG NG mixed mixed mixed example 3 phasephase phase comparative 0.002 0.01 0.20 1.008 NG NG NG NG NG NG NG NGexample 4 example 9 0.002 0.03 0.07 1.008 NG NG mixed mixed mixed mixedmixed mixed phase phase phase phase phase phase example 10 0.002 0.040.05 1.008 NG NG mixed mixed mixed mixed mixed mixed phase phase phasephase phase phase example 11 0.002 0.07 0.03 1.008 NG NG mixed mixedmixed mixed mixed mixed phase phase phase phase phase phase example 120.002 0.1 0.02 1.008 NG NG mixed mixed h-BT h-BT h-BT h-BT phase phaseexample 2 0.002 0.14 0.01 1.008 NG NG h-BT h-BT h-BT h-BT h-BT h-BTexample 13 0.002 0.2 0.01 1.008 NG NG mixed mixed h-BT h-BT h-BT h-BTphase phase comparative 0.002 0.25 0.01 1.008 NG mixed mixed mixed mixedmixed h-BT h-BT example 5 phase phase phase phase phase “h-BT” showsh-BaTiO₃ “mixed phase” shows two phases or more are identified amongh-BT, t-BT and c-BT.

TABLE 2 (Ba_(1−α)La_(α))_(A)(Ti_(1−β)Mn_(β))_(B)O₃ A site B site sub-Generating rate of h-BaTiO₃ [%] Sample substitution stitutionHeat-treating temperature No. amount α amount β α/β A/B 1000° C. 1050°C. 1100° C. 1150° C. 1200° C. 1250° C. 1300° C. 1350° C. comparative 00.14 0.00 1.000 100.0 100.0 100.0 100.0 100.0 100.0 example 2 example 10.002 0.14 0.01 1.006 95.9 100.0 100.0 100.0 100.0 100.0 example 2 0.0020.14 0.01 1.008 100.0 100.0 100.0 100.0 100.0 100.0 example 3 0.002 0.140.01 1.026 100.0 100.0 100.0 100.0 100.0 100.0 example 4 0.002 0.14 0.011.036 100.0 100.0 100.0 100.0 100.0 100.0 example 5 0.002 0.14 0.011.040 100.0 100.0 100.0 100.0 100.0 comparative 0.002 0.14 0.01 1.085example 1 example 6 0 0.14 0.00 1.008 98.2 99.3 100.0 100.0 100.0 100.0example 7 0.0012 0.14 0.01 1.008 100.0 100.0 100.0 100.0 100.0 100.0example 2 0.002 0.14 0.01 1.008 100.0 100.0 100.0 100.0 100.0 100.0example 8 0.0029 0.14 0.02 1.008 100.0 100.0 100.0 100.0 100.0 100.0comparative 0.07 0.14 0.50 1.008 42.0 41.5 42.2 example 3 comparative0.002 0.01 0.20 1.008 example 4 example 9 0.002 0.03 0.07 1.008 28.337.1 46.2 56.0 64.3 72.1 example 10 0.002 0.04 0.05 1.008 36.9 45.4 55.263.8 71.4 74.3 example 11 0.002 0.07 0.03 1.008 55.8 67.4 79.8 88.4 91.089.9 example 12 0.002 0.1 0.02 1.008 77.7 85.1 98.5 100.0 100.0 100.0example 2 0.002 0.14 0.01 1.008 100.0 100.0 100.0 100.0 100.0 100.0example 13 0.002 0.2 0.01 1.008 58.0 74.6 100.0 100.0 100.0 100.0comparative 0.002 0.25 0.01 1.008 24.2 34.9 48.4 59.0 84.8 100.0 100.0example 5

TABLE 3 (Ba_(1−α)La_(α))_(A)(Ti_(1−β)Mn_(β))_(B)O₃ A site B site sub-Specific surface area of obtained powder [m²/g] Sample substitutionstitution Heat-treating temperature No. amount α amount β α/β A/B 1000°C. 1050° C. 1100° C. 1150° C. 1200° C. 1250° C. 1300° C. 1350° C.comparative 0 0.14 0.00 1.000 1.6 — — — — — example 2 example 1 0.0020.14 0.01 1.006 5.1 3.1 1.0 — — — example 2 0.002 0.14 0.01 1.008 5.53.4 1.6 0.6 — — example 3 0.002 0.14 0.01 1.026 5.0 3.2 1.2 — — —example 4 0.002 0.14 0.01 1.036 4.7 3.0 1.1 — — — example 5 0.002 0.140.01 1.040 2.7 1.3 0.3 — — comparative 0.002 0.14 0.01 1.085 example 1example 6 0 0.14 0.00 1.008 5.3 3.4 1.0 — — — example 7 0.0012 0.14 0.011.008 5.0 4.0 1.2 1.6 — — example 2 0.002 0.14 0.01 1.008 5.5 3.4 1.60.6 — — example 8 0.0029 0.14 0.02 1.008 5.5 3.4 1.6 0.6 — — comparative0.07 0.14 0.50 1.008 example 3 comparative 0.002 0.01 0.20 1.008 example4 example 9 0.002 0.03 0.07 1.008 2.1 0.8 — example 10 0.002 0.04 0.051.008 2.7 1.4 0.6 — example 11 0.002 0.07 0.03 1.008 8.1 5.3 3.2 1.3 0.6— example 12 0.002 0.1 0.02 1.008 7.0 4.7 2.3 — — — example 2 0.002 0.140.01 1.008 5.5 3.4 1.6 0.6 — — example 13 0.002 0.2 0.01 1.008 4.8 2.51.1 — — — comparative 0.002 0.25 0.01 1.008 0.4 — — — example 5

From FIG. 2A to FIG. 2C, in the example 10, h-BaTiO₃, t-BaTiO₃ andc-BaTiO₃ were confirmed. Note that, t-BaTiO₃ and c-BaTiO₃ are notdistinguished because their peaks are close. Also, in the example 2,only a phase of the hexagonal barium titanate was confirmed.

In contrast, in the comparative example 1, a phase of bariumorthotitanate (Ba₂TiO₄) is confirmed near 2θ=29°, it was confirmed aphase other than barium titanate was generated.

From Table 1, when the heat-treatment temperature is lower, phases otherthan barium titanate (barium carbonate, barium orthotitanate and thelike) were identified as shown in FIG. 2C, thus it was confirmedundesirable tendency.

Also, when the A/B is too large, the “A” site substitution amount is toolarge and the “B” site substitution amount is too low, a phase otherthan barium titanate is identified, even though the heat-treatmenttemperature was risen. Thus it was confirmed that undesirable tendency.

In Table 2, samples to which h-BaTiO₃ generating rate was not measuredwere shown by diagonal line. From Table 2, when the “A” sitesubstitution amount is larger, or the “B” site substitution amount istoo low, h-BaTiO₃ generating rate becomes lower, thus it was confirmedundesirable tendency.

From Table 3, it was confirmed that when the A/B is 1.000, a specificsurface area of the hexagonal type barium titanate powder becomessmaller than 2 m²/g, which is not desirable tendency. Also, it wasconfirmed that hexagonal type barium titanate powder whose specificsurface area is 2 m²/g or more can be obtained by setting the “A” sitesubstation amount and “B” site substitution amount within a range of thepresent invention, and by controlling the heat-treatment temperatureappropriately.

In FIG. 3, particle size distributions of an example 2 and a sample ofpowder produced by heat-treating hexagonal barium titanate at 1500° C.and further pulverizing are shown. A specific surface area of theexample 2 was 5.5 m²/g. On the other hand, for the sample pulverizedafter heat-treatment, a specific surface area before pulverization(immediately after producing) was 0.9 m²/g, a specific surface area ofafter pulverization was 5.4 m²/g.

As it is clear from FIG. 3, the specific surface areas of both samplesare about same level, however, particle size distributions are quitedifferent, it was confirmed that the sample of the example can obtainsharp distribution. In contrast, even though the specific surface isincreased by pulverizing the powder immediately after producing, it wasconfirmed that the particle size distribution becomes broader, which isnot preferable.

Experimental Example 2

Except for using oxides, carbonate and hydroxide of elements shown inTable 4 as a raw material of the element “M” instead of La(OH)₃, apowder was produced as similar with the example 2, a specific surfacearea was measured and X-ray diffraction was performed. Results are shownin Tables 4 to 6.

TABLE 4 (Ba_(1−α)M_(α))_(A)(Ti_(1−β)Mn_(β))_(B)O₃ Identified phase by Asite B site X-ray diffraction Sample element substitution substitutionHeat-treating temperature No. “M” amount α amount β α/β A/B 1000° C.1050° C. 1100° C. example 2 La 0.002 0.14 0.01 1.008 NG NG h-BT example14 Ca 0.002 0.14 0.01 1.008 NG NG h-BT example 15 Sr 0.002 0.14 0.011.008 NG NG h-BT example 16 Dy 0.002 0.14 0.01 1.008 NG NG h-BT example17 Gd 0.002 0.14 0.01 1.008 NG NG h-BT example 18 Ho 0.002 0.14 0.011.008 NG NG h-BT example 19 Y 0.002 0.14 0.01 1.008 NG NG h-BT example20 Er 0.002 0.14 0.01 1.008 NG NG h-BT example 21 Yb 0.002 0.14 0.011.008 NG NG h-BT example 22 Ce 0.002 0.14 0.01 1.008 NG NG h-BT example23 Bi 0.002 0.14 0.01 1.008 NG NG h-BT Identified phase by X-raydiffraction Sample Heat-treating temperature No. 1150° C. 1200° C. 1250°C. 1300° C. 1350° C. example 2 h-BT h-BT h-BT h-BT h-BT example 14 h-BTh-BT h-BT h-BT h-BT example 15 h-BT h-BT h-BT h-BT h-BT example 16 h-BTh-BT h-BT h-BT h-BT example 17 h-BT h-BT h-BT h-BT h-BT example 18 h-BTh-BT h-BT h-BT h-BT example 19 h-BT h-BT h-BT h-BT h-BT example 20 h-BTh-BT h-BT h-BT h-BT example 21 h-BT h-BT h-BT h-BT h-BT example 22 h-BTh-BT h-BT h-BT h-BT example 23 h-BT h-BT h-BT h-BT h-BT “h-BT” showsh-BaTiO₃ “mixed phase” shows two phases or more are identified amongh-BT, t-BT and c-BT.

TABLE 5 (Ba_(1−α)M_(α))_(A)(Ti_(1−β)Mn_(β))_(B)O₃ Generating rate of Asite B site h-BaTiO₃ [%] Sample element substitution substitutionHeat-treating temperature No. “M” amount α amount β α/β A/B 1000° C.1050° C. 1100° C. example 2 La 0.002 0.14 0.01 1.008 100.0 example 14 Ca0.002 0.14 0.01 1.008 100.0 example 15 Sr 0.002 0.14 0.01 1.008 100.0example 16 Dy 0.002 0.14 0.01 1.008 100.0 example 17 Gd 0.002 0.14 0.011.008 100.0 example 18 Ho 0.002 0.14 0.01 1.008 100.0 example 19 Y 0.0020.14 0.01 1.008 100.0 example 20 Er 0.002 0.14 0.01 1.008 100.0 example21 Yb 0.002 0.14 0.01 1.008 100.0 example 22 Ce 0.002 0.14 0.01 1.008100.0 example 23 Bi 0.002 0.14 0.01 1.008 100.0 Generating rate ofh-BaTiO₃ [%] Sample Heat-treating temperature No. 1150° C. 1200° C.1250° C. 1300° C. 1350° C. example 2 100.0 100.0 100.0 100.0 100.0example 14 100.0 100.0 100.0 100.0 100.0 example 15 100.0 100.0 100.0100.0 100.0 example 16 100.0 100.0 100.0 100.0 100.0 example 17 100.0100.0 100.0 100.0 100.0 example 18 100.0 100.0 100.0 100.0 100.0 example19 100.0 100.0 100.0 100.0 100.0 example 20 100.0 100.0 100.0 100.0100.0 example 21 100.0 100.0 100.0 100.0 100.0 example 22 100.0 100.0100.0 100.0 100.0 example 23 100.0 100.0 100.0 100.0 100.0

TABLE 6 (Ba_(1−α)M_(α))_(A)(Ti_(1−β)Mn_(β))_(B)O₃ Specific surface areaof A site B site obtained powder [m²/g] Sample element substitutionsubstitution Heat-treating temperature No. “M” amount α amount β α/β A/B1000° C. 1050° C. 1100° C. example 2 La 0.002 0.14 0.01 1.008 5.5example 14 Ca 0.002 0.14 0.01 1.008 5.5 example 15 Sr 0.002 0.14 0.011.008 5.8 example 16 Dy 0.002 0.14 0.01 1.008 5.9 example 17 Gd 0.0020.14 0.01 1.008 5.3 example 18 Ho 0.002 0.14 0.01 1.008 5.2 example 19 Y0.002 0.14 0.01 1.008 5.3 example 20 Er 0.002 0.14 0.01 1.008 5.8example 21 Yb 0.002 0.14 0.01 1.008 5.9 example 22 Ce 0.002 0.14 0.011.008 5.3 example 23 Bi 0.002 0.14 0.01 1.008 5.5 Specific surface areaof obtained powder [m²/g] Sample Heat-treating temperature No. 1150° C.1200° C. 1250° C. 1300° C. 1350° C. example 2 3.4 1.6 0.6 — — example 142.8 1.0 — — — example 15 2.9 1.0 — — — example 16 3.0 0.9 — — — example17 2.8 0.8 — — — example 18 2.8 0.7 — — — example 19 2.9 1.0 — — —example 20 2.7 1.2 — — — example 21 3.1 1.7 — — — example 22 3.2 1.4 — —— example 23 3.2 1.1 — — —

From Tables 4 to 6, it was confirmed it tends to that similar with theexample 2, even if other elements other than La is used as the element“M”.

From the above, it was confirmed that the hexagonal type barium titanatepowder according to the present invention includes the hexagonal bariumtitanate as a main component and that the specific surface area thereofis 2 m²/g or more and thus particle size distribution thereof is narrow.

Experimental Example 3

After weighing the hexagonal type barium titanate powder and rawmaterials of subcomponents powder having an average particle diameter of0.1 to 1.5 μm (MgO, CaO, BaO, Mn₃O₄, CuO, Al₂O₃, Y₂O₃, Dy₂O₃, Gd₂O₃,Ho₂O₃, Yb₂O₃, Tb₂O₃ and SiO₂—ZnO—B₂O₃ glass) so that composition afterfiring satisfies the composition shown in Table 7, water was added as amedium to the raw materials and mixed by a ball mill during 5 hours.Then, the mixture was dried so that mixed powder was obtained.

Note that, the above mentioned hexagonal type barium titanate powder wasproduced as similar with the experimental example 1, except for using Laas the element “M”, and setting α, β and A/B in the generic formula toα=0, β=0.15 and A/B=1.008. Also, a specific surface area of thehexagonal type barium titanate powder by BET method was 5 m²/g, and ahexagonal barium titanate rate was 95%.

Dielectric layer paste was obtained by mixing 100 parts by weight of themixture powder after drying obtained from the above manner and 4.8 partsby weight of acryl resin, 40 parts by weight of methylene chloride, 20parts by weight of ethyl acetate, 6 parts by weight of mineral spiritand 4 parts by weight of acetone with a ball mill to make paste.

Also, 100 parts by weight of Ni particle, 40 parts by weight of organicvehicle (8 parts by weight of ethyl cellulose is dissolved to 92 partsby weight of butyl carbitol), 10 parts by weight of butyl carbitol weremade to paste by kneading with three roll mill so that an internalelectrode layer paste was obtained.

Also, 100 parts by weight of Cu particle, 35 parts by weight of organicvehicle (8 parts by weight of ethyl cellulose is dissolved to 92 partsby weight of butyl carbitol) and 7 parts by weight of butyl carbitolwere made to paste by kneading so that an external electrode layer pastewas obtained.

Next, a green sheet having 2.5 μm of thickness was formed on a PET film,after printing the internal electrode layer paste on the green sheet,the green sheet was removed from the PET film. Next, these green sheetsand a protective green sheet (internal electrode layer paste is notprinted) were stacked and bonded by pressure so that a green stackingbody was obtained. A number of stacking sheets having the internalelectrode were set as 100 layers.

Also, a green sheet having 6.5 μm of thickness was formed on the PETfilm by using the above mentioned dielectric layer paste, after printingthe internal electrode layer paste on the green sheet, and the greensheet was removed from the PET film. Next, these green sheets and aprotective green sheet (internal electrode layer paste is not printed)were stacked and bonded by pressure so that a green multilayer body wasobtained. A number of stacking sheets having the internal electrode wereset as 100 layers.

Next, the green stacking body was cut to a predetermined size andobtained a green chip, binder removal treatment, firing and reoxidationtreatment (annealing) were performed to the green chip so that amultilayer ceramic capacitor firing body was obtained. The binderremoval treatment was performed under a condition that a temperaturerising rate is 25° C./hour, a holding temperature is 260° C., a holdingtime is 8 hours under air atmosphere. Also, firing was performed under acondition that a temperature rising rate is 25° C./hour, a holdingtemperature is 1000° C., a holding time is 2 hours, a cooling rate is200° C./hour under wet N₂+H₂ mixture gas atmosphere (oxygen partialpressure is adjusted within 1×10⁻⁸ to 1×10⁻⁶ Pa). The reoxidationtreatment was performed under a condition that a holding temperature is900° C., a temperature holding time is 2 hours, a cooling rate is 200°C./hour under wet N₂ gas atmosphere (oxygen partial pressure is 1×10⁻²to 1 Pa). Note that, for wetting the atmosphere gas when firing andannealing, a wetter is used wherein a water temperature was set at 35°C.

Next, after polishing an end face of the multilayer ceramic firing body,an external electrode paste was transferred to the end face, fired, at900° C. during 60 minute in wet N₂+H₂ atmosphere so as to form anexternal electrode, and a sample of multilayer ceramic capacitor havingconstitution shown in FIG. 1 was obtained. Next, Sn plating film and Niplating film were formed on an external electrode surface so that asample for measuring was obtained.

A size of the respective sample obtained as above is 3.2 mm×1.6 mm×1.6mm, a number of dielectric layer sandwiched by the internal electrodelayers was 100, a thickness of the internal electrode layer was 2 μm.The above property evaluation was made for each of the samples. Also,results for measuring temperature dependency of the specificpermittivity with respect to capacitor samples produced in an example 51and an example 59 are shown in FIG. 4.

TABLE 7 Mn₃O₄ and/or Insulation Sample Rare Cr₂O₃ Glass Q resistance No.earthes MgO CaO BaO Mn₃O₄ Cr₂O₃ CuO Al₂O₃ component ε value [Ω] example51 Y:1.0 2.0 1.0 1.0 1.0 0.0 0.5 0.8 0.10 86 1126 1.58E+12 example 52Y:1.0 3.5 2.0 1.0 1.5 0.0 0.7 0.7 0.50 81 1256 1.16E+12 example 53 Y:1.05.0 5.0 5.0 2.0 0.0 0.8 0.5 1.00 78 1299 2.01E+12 example 54 Y:3.0 1.02.0 1.0 1.0 0.0 0.5 0.8 0.10 72 1488 3.26E+12 example 55 Y:3.0 3.5 2.01.0 1.5 0.0 0.7 0.7 0.50 66 1504 3.50E+12 example 56 Y:3.0 5.0 5.0 5.00.0 2.0 0.8 0.5 1.00 62 1566 3.00E+12 example 57 Y:5.0 1.0 1.0 2.0 1.00.0 0.5 0.8 0.10 65 1524 3.59E+13 example 58 Y:5.0 3.5 2.0 1.0 1.5 0.00.7 0.7 0.50 55 1687 5.93E+13 example 59 Y:5.0 5.0 5.0 5.0 1.0 1.0 0.80.5 1.00 51 1864 2.29E+13 example 60 Dy:0.5, 2.0 1.0 1.0 1.0 0.0 0.5 0.80.10 70 1109 2.59E+12 Gd:0.5 example 61 Ho:0.5, 3.5 2.0 1.0 1.5 0.0 0.70.7 0.10 85 1087 2.31E+12 Yb:0.5 example 62 Y:1.0 0.5 5.0 5.0 1.0 0.00.5 0.8 0.10 102 1023 1.58E+12 example 63 Y:1.0 5.0 0.5 5.0 1.5 0.0 0.70.7 0.50 87 1148 1.16E+12 example 64 Y:1.0 5.0 5.0 0.5 2.0 0.0 0.8 0.51.00 93 1036 2.01E+12 comparative Y:0 1.0 1.0 1.0 1.0 0.0 0.5 0.8 0.1065 732 3.59E+11 example 51 comparative Y:1.0 5.0 5.0 6.0 1.5 0.0 0.7 0.70.50 41 1256 2.12E+13 example 52 comparative Y:1.0 3.5 2.0 6.0 2.5 0.00.7 0.7 0.50 39 1256 2.12E+13 example 53 comparative Y:1.0 3.5 2.0 6.00.0 0.0 0.7 0.7 0.50 86 964 2.59E+11 example 54 comparative Y:5.0 3.52.0 6.0 1.5 0.0 0.7 0.7 2.00 34 1864 1.16E+12 example 55 comparativeY:5.0 1.0 3.0 3.0 0.3 0.0 0.4 0.3 0.00 — — — example 56 Contents of MgO,CaO and BaO are shown in terms of oxide Contents of Mn₃O₄, Cr₂O₃, CuOand Al₂O₃ are shown in terms of metal element Contents of glasscomponent are shown in terms of SiO₂ In table, “mE + n” shows “m ×10^(n)”

Property evaluation for capacitor cannot be made to a comparativeexample 56 due to poor sintering.

Experimental Example 4

Contents of subcomponents, with respect to 100 moles of the maincomponent, were set as 0.1 mole of rare earth, 1.0 mole of MgO, 1.0 moleof CaO, 1.0 mole of BaO, 0.5 mole of Mn₃O₄, 0.5 mole of CuO, 0.5 mole ofAl₂O₃ and 0.1 mole of glass component, and kinds of the element “M”, α,β and A/B in the generic formula were set as shown in Table 8. Exceptfor the above, a capacitor was produced as similar with the experimentalexample 3, the above mentioned property evaluation was performed.Results are shown in Table 8.

Experimental Example 5

Contents of subcomponents, with respect to 100 moles of the maincomponent, were set as 5.0 moles of rare earth, 5.0 moles of MgO, 5.0moles of CaO, 5.0 moles of BaO, 2.0 moles of Mn₃O₄, 2.0 moles of CuO,2.0 moles of Al₂O₃ and 1.0 mole of glass component, and kinds of theelement “M”, α, β and A/B in the generic formula were set as shown inTable 9. Except for the above, a capacitor was produced as similar withthe experimental example 3, the above mentioned property evaluation wasperformed. Results are shown in Table 9.

TABLE 8 A site B site Insulation Sample element substitutionsubstitution resistance No. “M” amount α amount

A/B ε Q value [Ω] example 71 La 0 0.03 1.008 80 1088 1.22E+12 example 72La 0 0.20 1.008 61 1147 3.13E+12 example 73 La 0.0025 0.03 1.008 95 10031.01E+12 example 74 La 0.0025 0.20 1.008 72 1115 2.11E+14 example 75 La0.0010 0.15 1.001 67 1100 2.81E+12 example 76 La 0.0010 0.15 1.040 701077 1.87E+12 example 77 La 0.0020 0.05 1.008 88 1061 1.65E+12 example78 La 0.0020 0.15 1.008 80 1110 1.78E+12 example 79 La 0 0.15 1.006 761040 2.20E+12 example 80 La 0 0.15 1.036 78 1019 2.01E+12 example 81 Dy0 0.15 1.008 66 1072 2.36E+12 example 82 Ho 0 0.15 1.008 66 10992.40E+12 example 83 Y 0 0.15 1.008 63 1102 2.58E+12 example 84 Er 0 0.151.008 64 1098 2.51E+12 example 85 Yb 0 0.15 1.008 62 1105 2.66E+12example 86 Ce 0 0.15 1.008 75 1051 2.24E+12 example 87 Bi 0 0.15 1.00892 1022 1.89E+12 0.1 mol of rare earth in terms of rare earth element,0.1 mol of MgO, 1.0 mol of CaO, 1.0 mol of BaO respectively in terms ofoxide, 0.5 mol of Mn₃O₄ in terms of metal element, 0.5 mol of CuO interms of metal element, 0.5 mol of Al₂O₃ in terms of metal element, 0.1mol of glass component in terms of SiO₂ with respect to 100 mol of amain component. mE + n” shows “m × 10^(n)”

indicates data missing or illegible when filed

TABLE 9 A site B site Insulation Sample element substitutionsubstitution resistance No. “M” amount α amount

A/B ε Q value [Ω] example 91 La 0 0.03 1.008 61 1186 2.81E+12 example 92La 0 0.20 1.008 50 1288 4.01E+12 example 93 La 0.0025 0.03 1.008 68 11472.15E+12 example 94 La 0.0025 0.20 1.008 60 1211 2.99E+12 example 95 La0.0010 0.15 1.001 52 1305 3.14E+12 example 96 La 0.0010 0.15 1.040 551313 3.23E+12 example 97 La 0.0020 0.05 1.008 72 1131 2.00E+12 example98 La 0.0020 0.15 1.008 67 1156 2.31E+12 example 99 La 0 0.15 1.006 601192 2.28E+12 example 100 La 0 0.15 1.036 58 1202 2.67E+12 example 101Dy 0 0.15 1.008 57 1222 2.73E+12 example 102 Ho 0 0.15 1.008 52 12152.88E+12 example 103 Y 0 0.15 1.008 53 1189 2.79E+12 example 104 Er 00.15 1.008 52 1241 2.85E+12 example 105 Yb 0 0.15 1.008 52 1203 2.80E+12example 106 Ce 0 0.15 1.008 55 1190 2.73E+12 example 107 Bi 0 0.15 1.00867 1133 2.15E+12 5.0 mol of rare earth in terms of rare earth element,5.0 mol of MgO, 5.0 mol of CaO, 5.0 mol of BaO respectively in terms ofoxide, 2.0 mol of Mn₃O₄ in terms of metal, element, 2.0 mol of CuO interms of metal element, 2.0 mol of Al₂O₃ in terms of metal element, 1.0mol of glass component in terms of SiO₂ with respect to 100 mol of amain component. mE + n” shows “m × 10^(n)”

indicates data missing or illegible when filed

From the above, according to the dielectric ceramic composition havingthe hexagonal type barium titanate of the present invention as a mainphase, electronic components such as a ceramic capacitor showingcomparatively high specific permittivity, having advantageous insulationproperty and having sufficient reliability are obtained.

1. A hexagonal type barium titanate powder comprising barium titanate as a main component shown by a generic formula of (Ba_(1-α)M_(α))_(A)(Ti_(1-β)Mn_(β))_(B)O₃ and having hexagonal structure wherein; an effective ionic radius of 12-coordinated “M” is −20% or more to +20% or less with respect to an effective ionic radius of 12-coordinated Ba²⁺, and said A, B, α and β satisfy relations of 1.000<(A/B)≦1.040, 0≦α<0.003, 0.03≦β≦0.2.
 2. The hexagonal type barium titanate powder as set forth in claim 1, wherein; a ratio of said α and said β satisfies relation of (α/β)≦0.40.
 3. A dielectric ceramic composition comprising a hexagonal type barium titanate as a main component shown by a generic formula of (Ba_(1-α)M_(α))_(A)(Ti_(1-β)Mn_(β))_(B)O₃ and having hexagonal structure wherein; an effective ionic radius of 12-coordinated “M” is −20% or more to +20% or less with respect to an effective ionic radius of 12-coordinated Ba²⁺, and said A, B, α and β satisfy relations of 1.000<(A/B)≦1.040, 0≦α<0.009, 0.03≦β≦0.2, and as subcomponents, with respect to 100 moles of the main component, 2 to 5 moles of at least one of alkaline earth oxide selected from a group consisting of MgO, CaO and BaO in terms of respective oxides, and a total content of said alkaline earth oxides is 15 moles or less; 0.5 to 2 moles of Mn₃O₄ and/or Cr₂O₃, and CuO and Al₂O₃ in terms of respective metal elements; 1 to 5 moles of at least one of oxides of rare earth element selected from a group consisting of Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Yb in terms of total of rare earth element; and 0.1 to 1 mole of glass component including SiO₂ in terms of SiO₂.
 4. An electronic component comprising a dielectric layer composed of the dielectric ceramic composition as set forth in claim 3 and an internal electrode layer.
 5. A method of producing the hexagonal type barium titanate powder as set forth in claim 1 comprising steps of; preparing at least a raw material of barium titanate and a raw material of Mn, and heat-treating said raw material of barium titanate and said raw material of said Mn.
 6. A method of producing the hexagonal type barium titanate powder as set forth in claim 2 comprising steps of; preparing at least a raw material of barium titanate and a raw material of Mn, and heat-treating said raw material of barium titanate and said raw material of said Mn. 